Chronic bronchitis: the antiproteinase/proteinase balance and the effect of infection and corticosteroids.

Proteolytic enzymes have the potential to destroy many of the lung structures, provided that their activity exceeds the capacity of their natural inhibitors. Neutrophil elastase has been implicated in the pathogenesis of chronic bronchitis and is regularly present in secretions from these patients. Several factors, including infection and inhibitor deficiency, influence the balance between enzymes and inhibitors and may play a role in disease progression. Many enzymes and inhibitors are found in lung secretions and further study of their interactions and effect on lung tissues will clarify the nature and clinical effect of chronic bronchitis.